1. Field Of The Invention
The invention relates to a measuring apparatus, and more particularly a scale-type weighing apparatus wherein a sensor produces a digital value output signal which directly represents the measured quantity and its units of measure displayed on a visual display readout device disposed physically separate from the sensor and connected to the sensor by a signal line and which has an identification plate which serves as a display means for the technical measurement parameters of the sensor.
2. Description Of The Prior Art
When such measuring apparatuses are used in commerce where calibration is a requirement, it is not only advantageous but also mandatory, under national and international calibration regulations, that the identification plate with the technical measurement parameters be mounted in proximity to the display device which displays the measured quantities. In a weighing apparatus, for example, the parameters include data on the maximum load, the scale division on the display, the tare range, i.e., range of weights for which the scale can be set to subtract a tare, etc. However, there is also a requirement that the particular identification plate be unambiguously associated with the given sensor. Accordingly, in known measuring apparatuses there cannot be provision for breaking the connection between the sensor and the readout device, which connection is supplied solely by the signal line. If any releasable couplings exist between the signal line and the readout device, these must be sealed with lead, in known measuring apparatuses. If the coupling is broken, the lead seal is destroyed, which, according to regulation, necessitates recalibration, because the connection between the components has been broken. Therefore in order to avoid recalibration, one must always handle the entire measuring apparatus as a connected unit, which in practice has a number of disadvantages, particularly if the readout device or the weighing bridge containing the sensor is movable from location to location.
The inconvenience of recalibrating is particularly presented if the weighing bridge containing the sensor, or the readout device, develops a malfunction and must be replaced. In this case, various lead seal locations must be disturbed, following which the entire apparatus must be recalibrated and re-sealed with lead seals. This is very costly and consumptive of time and resources, particularly with large scales in the heavy load range of 500 kg or more. Moreover, there are substantial problems which arise in the case of a composite scale comprised of a plurality of weighing bridges each of which includes a sensor, which bridges are connected to a single readout device.
Another disadvantage is present in weighing apparatuses wherein the weighing bridges which contain the sensors are mounted in a cavity ("well") at a depressed level, so as to be inaccessible at ground level. In order to gain access to the lead seal locations on the sensors, to check whether the lead seals in the well have been disturbed, in general it is necessary to remove the heavy weighing plate. Thus there is a need for means whereby the lead seal locations are disposed outside the region of the weighing bridge, in a readily accessible place.